In the production of microcomputers the finished products are subjected to testing operations, in order to check on their functionality.
Generally microcomputers have memories within them of not inconsiderable size, and the checking time depends on the size of the memory. The checking time also depends on the type of memory to be checked, and a minimum of three readings is required for a ROM (READ ONLY MEMORY) and a maximum of sixteen readings for an EPROM (ERASABLE READ ONLY MEMORY). It can be seen that checking operations involve problems of time and cost, especially because they are executed on very expensive machines.
With the current checking devices and procedures, based on programs formed by instructions, that require a discrete time for the process of reading any information contained in the memory, testing times are very long and involve substantial increases in production costs.